Servicing your +2’s Datacorder

If you’re beginning to witness the terror of R Tape loading error when loading a game into your +2, then it’s probably time to give the datacorder mechanism a service.

The techniques for doing so are broadly the same as for most tape recorder mechanisms, since the datacorder’s mechanical components are sourced from cheap mono tape decks (and the same mechanism has been found in at least one Academy tape recorder).

However there are some common remedies for certain types of fault, and I’ll detail these below.

General Cleanup and Azimuth Adjustments

Azimuth adjustment hole visible in the case plastics, tape head visible in the centre and capstan/roller to the right.

If the audio playback sounds steady and doesn’t seem to change speed, then you may get away with cleaning the tape head, capstan and pinch roller, as these parts tend to pick up lots of dirt and magnetised tape particles after years of use.

This can be done with some IPA (Isopropanol alcohol, not ale!) and cotton buds.

If a thorough clean doesn’t improve matters, then the next step will be to adjust the azimuth of the tape head.

As a term, azimuth angle is just a fancy name for the relationship between the tape head and the magnetic tape in the cassette itself. For audio recordings it’s desirable that this is adjusted to be as close to 90 degrees as possible.

There is a small hole in the +2’s case to allow such adjustments without disassembling the computer, suitable for a No. 0 jewellers screwdriver.

Perform this adjustment with a tape running so you can hear the clarity of the audio change with adjustments, until you achieve the clearest audio possible.

More indepth servicing

Twin belt mechanism as found in the Grey +2

If the speed at which your audio plays back varies significantly, or the datacorder has difficulty fast forwarding or rewinding cassettes, then it’s probably time to change the drive belts on the mechanism. This is fairly straightforward, but there’s one caveat – the drive mechanism changes between grey +2’s and black +2A/+2B machines. The grey +2 mechanism uses twin belts, whereas the +2A mechanism uses a single drive belt.

Single belt mechanism as found in the +2A and +2B machines.

Replacement belt kits can be obtained from Dataserve Retro, and they can be alternatively be sourced from Farnell – the large belt which fits both the grey +2 and black +2A main drive, and the smaller belt required for the grey +2.

To replace the belts, remove the six screws holding the case together and separate the top and bottom halves of the machine by disconnecting the keyboard ribbons and the tape deck connector. Lay the top half of the machine on your workspace, keys down and you should now be able to see the cassette mechanism.

Remove the belt(s) with a tweezers and install the replacements, ensuring the belt isn’t twisted once installed. For twin belt mechanisms, install the smaller (lower) belt first.

Pause mechanism issues

Close up of flywheel, showing the pause mechanism parts in white directly underneath it

If you still have problems with speed fluctuations after replacing the drive belts, then try moving the large flywheel with your finger, and check if it is fouling on the white plastic latch below that forms part of the pause mechanism.

The white ‘hat’ piece is a push fit onto the plastic pillar that supports it and the moving latch piece beneath. There’s a spring internal to this that allows the latch piece to ‘float’ and move cleanly, and if the hat piece deteriorates it can crack, allowing the spring to push it against the flywheel.

Tape capstan, with circlip highlighted.

To remedy this you’ll need to remove the flywheel by first removing a small circlip on the topside of the mechanism. The flywheel can then be removed from the underside of the mechanism (be careful not to lose the tiny washers, or the pause mechanism hat, spring and latch themselves!)

Dab a little superglue on the inside of the hat piece, and then replace, with spring and latch, back on to the plastic pillar and hold in place until the glue has set. You can then replace the flywheel and circlip, and check that the hat piece now clears the flywheel.

Recapping the Tape PCB

You may find that the audio quality can’t be improved by setting the azimuth angle or by cleaning the tape head, so at this point you may need to replace the capacitors on the tape PCB.

Even though there are two distinct tape mechanisms, there are actually three distinct tape PCB types – the PCB on the UK made grey +2 differs greatly from that in the Taiwanese made model. The cap values are the same but most are axial on the UK model, as opposed to radial on the Taiwanese made machine.

The best method for gaining access to the PCB for recapping is to remove it entirely from the machine case – there are four screws holding the mechanism to the top casing, another two screws holding the motor, and one final screw holding the LED board in place which is attached to the tape PCB.

Once free of the case, there are two additional screws holding the PCB to the mechanism which can be removed so you can flip the PCB upside down to access the capacitors.

The replacement caps needed differ according to the machine the mechanism comes from, and are given below (note the swapping of values between C318 and C324 on the grey +2 mechanisms). Voltage ratings given are minimum values.

Fixing Mains Hum on Audio

Taiwanese made Grey +2’s seem to suffer more than most from poor grounding, which manifests itself as buzzing or humming on the audio output. Since the audio output is active even when the Datacorder isn’t running, this hum ends up being present all of the time.

Tape PCB showing installation of ground wire

The tape PCB uses the metal frame of the tape mechanism as a means of routing ground paths to different sides of the PCB, so the first thing to check is that the two screws used to attach the PCB to the mechanism are tight and conductive.

The above usually fixes the problem, but the addition of a ground wire between two points on the PCB as shown is no harm and is a much more reliable solution.